Production of gasoline



Jan. 11, 1949. COLE 2,458,980

PRODUCTION OF GASOLINE Filed Dec. 8, 1945 Per Cen? Saruranon v o w E\nvenror loberf MCole 59 his Afl'orneg 4% Patented Jan. 11, 1949.PRODUCTION oricliso RobertMiGolamakland, catfzgs sigttrtashat g,Development Company, gSan Francisco, acahfi, acorporation of Delaware 7Application Deceniber 8, 1-945, Serial Nos633t8I4 :cf catalyticmethodsthe most important means 2 Glaims. (all es-+30) "This "inventionrelates to the production of hi'gh-octane leaded :gasolines from.thermal gasoline stocks.

of producing high-=octane gasolinesis by thermal methods; that is, bythe thermal cracking of higher boiling oils (Dubbs, De Florez, Cross,"Holmes Manley,'T. V.-P.1processe's) andyor the thermal reforming of lowoctanegasoline stocks.

These processes give highly olefinic gasolines having"octane numbersgenerally between about 65 and 74. "These octane'ratings are notsufiiciently 'high to produce" the maximum quantities of finished"gasoline meeting the present requirements.

(The octane number' requirements for most automobile motors hasgraduallydncreased and is now ber couldbeproduced by these thermal.methods.

numbers of these stocks. Consequently,.it is the practice to=- obtainthe required octane rating of these stocks by the addition of tetraethyl lead (T. E. L.). In general," the desired octane numabout '75.)Thermal stocks of. higher octane num- :ber itl-islusual l-y rec mm-ndedto efiectrthe hydrogenation at a relatively high temperatureto .obtainacertain :amount of catalytic reforming simultaneously with the.hydrogenation. However, hydrogenation lat reforming temperatures is!coupled with-shortlcatalyst life; and :greater eX- pens-e-and.- is notentirely satisfactory.

.Ithasbeen fOH'IIdJ-thatiiH the refining of thermal gasoline-stocks (i..e.-:olefinic,;gasoline stocks produced tby thermal methods. :such inparticular as rthermal. cracking and thermal reforming) by.hydrogenationthe octane=number=of the product goesthr.ough- -amaximumras theipercentage of saturation (it e. then-percent 1 decreasein bromine :number due to hydrogenation) is-increased and then declineseat razrrelatively rapid rate. This point of maximumoctane number occursatla relaitivelylowsperceritage of saturation. The hydrogenation can .bemarried tout to this point of .120 .maximurrr octane number *and ;theoctane number of vthe--refined; product increased to the desiredleveltby the additionof T.:E.'L. It has now :been 1 found, Yhowever,that this :method of operationais not.the-most-advantageous. It has beenas tfoundnthattthe optimum saturation to be effected ber of the leadedproduct is appreciably above the 'octane'ratin'g or themarketed'ga'solinein'order to compensate for a certainamouritdfblendedlow-octane components, such .insparticular as straight-run gasoline. Theamount and quality of the. low-octane components -to be blended.thereforeilargely control the octane number-re- .quired of the leadedthermal gasoline in order .tmmeet the prevailing octanenumberspecifications.

These thermal gasoline stocks are quite highly unsaturated and requireconsiderable refining be- .fore they can be leaded. and blended. Theymay be refined by any one of a number of refining treatments such'asthe'conventional treatments .withsulfuric acid .or clay, .but thesetreatments A:-preferred method a for refining: such thermahstocksisbyt'hydrogenaincur." large refining losses.

tion. A hydrogenation treatment destroys the small amounts of diolefinsand other gum-forming constituents with substantially no treatinglosses. While very mild treatment has been quite successful in somecases it has been frequently reported that refining by hydrogenationresults in an excessive depreciation of the octane number of the stock.This has been postulated to be due to the hydrogenation of olefins. Inorder to counteract this depreciation of the octane numby: the:hydrogenation ttreatm'ent is a function of the desired octane number ofthe finished product and does nottcorrespond 1 to this maximumoctane-number. .v i

Accordingkito theaprocess'of thepresentinvention.thermalrgasolin'ewstocks from petroleum are ,hydrogenated.toranzoptimurmsaturation which is @afunction .ofi'and lidependent upon the desired.octane.'numbertof'theeleaded product. Stated in another way,the-hydrogenationisLcarried out to a specific degree of saturation whichallows a refined product of any given -desired octane number "to :be 1obtained with "the minimum amount :o'f TfiEJL. Therelationship betweenthe optipercentagewf saturation'oS) and the desired octane 'number isgiven approximately by r wherein 'Sis thejpercent saturation ashereinbenumber of the thermal stock treated, and i5 is a small allowablevariation to allow for slight differences between difierent feed stocks.

In order that the invention may be better understood, reference is hadto the attached drawing wherein there is shown by means of a graph thechange in ASTM octane number of a 400 end point cracked gasoline fromDubbs cracking rises relatively sharply to a maximum and then dropssharply with increasing saturation so that at complete saturation theoctane number has fallen over 18 points. Similar curves can bedetermined for leaded gasolines produced from such cracked gasolinestocks. However, the maximum points of the curves for various particularmaximum octane numbers, corresponding to minimum T. E. L. requirements,shift to the right with increasing octane number requirements. The pathof this shift is expressed by the above-given formula. a

The process of the invention is generally applicable for theproduction'of leaded gasoline from thermal gasoline stocks such asdescribed above. Such stocks have bromine numbers of at least 50. Thehydrogenation of the thermal gasoline stocks may be carried out with anyof the hydrogenation catalysts commonly used for the hydrogenation ofpetroleum fractions. Particularly suitable catalysts are tungstensulfide, nickel sulfide, molybdenum sulfide, tungsten sulfide promotedwith a sulfide of iron, cobalt or nickel, and cobalt molybdate. Variousother suitable catalysts are discussed in U. S. Paten No. 1,890,434 andBritish Patent 335,511.

The hydrogenation may be carried out with the gasoline stock in thevapor: phase,in the liquid phase, or in mixed phase, and undervarious'conditions of temperature, pressure and space velocity commonlyused for hydrogenation of gasoline stocks. The temperature, for example,may be advantageously between 400 and 850 F. and the pressure may beadvantageously between 100 and 1000 p. s. i. may be controlled-bycontrol of any one or combination of the operating variables such as thecatalyst activity, space velocity, temperature and pressure. A preferredvariable for control is the liquid hourly space velocity either alone orin combination with hydrogen pressure. The conditions, in any case, areso controlled for the individual catalyst,-feed stock and desired octanenumber that the bromine number is decreased by an amount satisfying theabove equation.

Example I A California pressure distillate fraction boiling essentiallybetween 110 F. and 210 F. and having a bromine number of 92 washydrogenated with a nickel sulfide-tungsten sulfide catalyst in whichthe nickel sulfide was the predominant constituent. The temperature was700 F.; the pressure was 700 p. s. i., and the molal ratio of recycledgas (largely hydrogen) to hydrocarbon 60 feed was about 7:1. The liquidhourly space velocity was varied between 10 and 55 to obtain The degreeof saturation the desired percent saturation. The original ASTM octanenumber was 73.8. The maximum clear ASTM octane number occurred when thesaturation was carried to about 8%. However, for a gasoline of ASTMoctane number of 77 the optimum saturation was found to be about 7%. Fora gasoline of ASTM octane number of 75 the optimum saturation was foundto be about 14%.

Example II A thermally cracked gasoline boiling essentially between 200F. and 300 F. and having a bromine number of 87.2 and an ASTM octanenumber of 70.4 washydrogenated at temperatures between 700 and 800 F.,pressure between 426 and 625 p. s. i., molal ratio of recycled gas(largely hydrogen) to hydrocarbon feed of about 7:1 and liquid hourlyspace velocities between 2.0 and 27.4 to control the percent saturation.It was found that the maximum clear ASTM octane number occurred 1 atabout 9% saturation. However,

when a gasoline of 75 ASTM octane number was desired it was found thatthe optimum saturation was about 32%. When a gasoline of 73 ASTM octanenumber was desired the optimum saturation was found to be about 21%.

I claim as my invention:

.1. Ina process for the production of a leaded gasoline having animproved ASTM octane number from a thermal gasoline stock having an ASTMoctane number N by hydrogenation of said thermal gasoline stock andaddition of tetraethyl-lead, the improvement which comprises ,carrying'out the hydrogenation of the thermal asoline stock under conditionsto effect such a percentage saturation of the stock S thatS='11+4.7(N'-N) :5 wherein N is the desired ASTM octane number of thehydrogenated and leaded product.

2. Process according to claim 1 in which the hydro enation is carriedout at a temperature between about 400 F. and 850 F. and the percentagesaturation is controlled by varying the space velocity.

ROBERT M. COLE.

file of this patent:

UNITED STATES PATENTS Number Name Date 2,202,401 ROSBIl n; May 28, 194:02,367,527 Ridgway Jan. 16, 1945 "2,371,355 ROSS 6t a1. Mar. 13, 19452,382,910 Pinkston Aug. 14, 1945 I FOREIGN PATENTS Number Country Date423,001 Great Blitaill Jan. 23, 1935 OTHER REFERENCES ll me 'Congr.mond. Petrole, vol. 2, pages 271-275 (1937) (article by Kudo et al., 0nthe Hydrogenation of Cracked Gasoline").

